u-boot-brain/arch/arm/mach-at91/bootparams_atmel.S

/*
 * Atmel SAMA5Dx boot parameter handling
 *
 * Copyright (c) 2016 Marek Vasut <marex@denx.de>
 *
 * SPDX-License-Identifier:	GPL-2.0+
 */

#include <asm-offsets.h>
#include <config.h>
#include <asm/system.h>
#include <linux/linkage.h>

ENTRY(save_boot_params)
	ldr	r0, =bootrom_stash
	str	r4, [r0, #0]
	b	save_boot_params_ret
ENDPROC(save_boot_params)
ARM: sama5d2: Implement boot device autodetection Implement support for saving ARM register R4 early during boot using save_boot_params . Implement support for decoding the stored register R4 value in spl_boot_device() to obtain boot device from which the SoC booted. This way, the SPL will always load U-Boot from the same device from which the SPL itself booted instead of using hard-coded boot device. This functionality is useful for example when booting sama5d2-xplained from SD card, where by default the SPL would try loading the U-Boot from eMMC and fail. This is because eMMC is on SDHCI0 (BOOT_DEVICE_MMC1), while SD slot is on SDHCI1 (BOOT_DEVICE_MMC2) and the SPL was hard-wired to always boot from BOOT_DEVICE_MMC1. Signed-off-by: Marek Vasut <marex@denx.de> Cc: Andreas Bießmann <andreas.devel@googlemail.com> Cc: Wenyou Yang <wenyou.yang@atmel.com> Reviewed-by: Andreas Bießmann <andreas@biessmann.org> 2016-04-23 04:56:21 +09:00			`/*`
			`* Atmel SAMA5Dx boot parameter handling`
			`*`
			`* Copyright (c) 2016 Marek Vasut <marex@denx.de>`
			`*`
			`* SPDX-License-Identifier: GPL-2.0+`
			`*/`

			`#include <asm-offsets.h>`
			`#include <config.h>`
			`#include <asm/system.h>`
			`#include <linux/linkage.h>`

			`ENTRY(save_boot_params)`
			`ldr r0, =bootrom_stash`
			`str r4, [r0, #0]`
			`b save_boot_params_ret`
			`ENDPROC(save_boot_params)`